Power systems worldwide need to ensure voltage regulation, stability, allow high levels of power transmission capacity in the lines to transfer power from existing or new generating sources, and regulate system frequency, despite various system disturbances. These disturbances could be slow and gradual variations in loads and generation, or large and sudden variations, such as faults, line switching, equipment outages, etc.
There are primarily two types of stability:
Angle Stability: This relates to maintaining synchronism of generators. It has two main components:
                a) Small Signal Stability—caused by small disturbances and insufficient damping in power systems with respect to different oscillatory modes        b) Transient Stability—This is affected by large disturbances in power systemsVoltage Stability: This relates to the system's ability to maintain acceptable voltages, and is typically caused by lack of adequate reactive power support both during steady state and during disturbances such as faults.        
Another major problem being increasingly encountered is the lack of power transfer capacity in transmission and distribution lines. Increasing stability significantly increases the power transmission capacity of transmission lines. On the other hand, the power transfer capacity in distribution lines is typically limited by thermal limits of the line.
A third problem being faced by power systems is the regulation of system frequency despite the ongoing system disturbances. Frequency deviations occur due to imbalances between the generation and the loads during disturbances. Maintaining frequency is an important issue in isolated power systems, such as microgrids.
Another issue with current technology is the lack of power carrying capacity in power transmission lines. With the ever-growing number of renewable generating sources in power transmission and distribution grids, there is an imminent need for providing capacity on existing lines to carry the real power generated by them.
The existing technology for compensating for reactive power flows in the lines is through passive devices such as capacitors and inductors, which are fixed in rating, and hence not controllable. Therefore, this method is not widely employed due to these limitations.
The other option is to install very expensive dynamic reactive power compensators such as Static Var Compensator (SVC) or Static Synchronous Compensator (STATCOM). These may not be cost-effective for the objective to be achieved.
Based on the above, there is therefore a need for systems, methods, and devices which mitigate if not overcome the issues noted above. More specifically, since photovoltaic (PV) solar farms conventionally only produce real power, and do not contribute to increasing system stability, enhancing power transfer capacity, or providing frequency control, methods and systems which would allow PV energy farms to perform these functions would be desirable.